The present disclosure is applicable to Orthogonal Frequency Division Multiple Access (OFDMA) system such as 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) and other similar systems.
The OFDMA systems such as 3GPP LTE optimize the system throughput by adjusting the transmit powers of a Reference Signal (RS) for channel estimation and data signal per user (or User Equipment (UE)).
In the legacy OFDMA-based system such as 3GPP LTE, the UE needs the channel information for data demodulation. Accordingly, the base station transmits the pilot signals, which are mapped to the Resource Element (RE) close to REs to which the data signals are mapped. The pilot signal is the signal known to the UE for use in the UE's channel estimation. The pilot signal is also referred to as the reference signal.
FIG. 1 is a diagram illustrating a configuration of transmit powers of the pilot and data signals according to the related art.
Referring to FIG. 1, the transmit powers of the data signal (Pdata) and the pilot signal (Ppilot) may differ from each other in level.
The UE demodulates a data signal using a channel estimated based on the pilot signal. For correct demodulation, the UE must acquire the information on the transmit powers on the pilot and data signals. Accordingly, the base station sends the UE the information on the pilot and data signal transmit powers. For example, the base station may send the UE a power ratio between the RE to which the pilot signal for channel estimation is mapped and the RE to which the data signal is mapped, i.e., power ratio information.
This is the method adapted to the 3GPP LTE in which the UE receives the information on the transmit power ratio between the RE for data signal transmission and the RE for pilot signal transmission.
FIG. 2 is a diagram illustrating the power ratio information transmission of the base station according to the related art.
Referring to FIG. 2, according to the LTE standard, the ratio between the transmit power at the Physical Downlink Shared Channel (PDSCH) RE and the transmit power at the Cell-specific Reference Signal (CRS) RE in the OFDM symbol carrying no CRS is defined as ρA. Likewise, the ratio between the transmit power at the PDSCH RE and the transmit power at the CRS RE in the OFDM symbol carrying CRS is defined as ρB. As shown in FIG. 2, the base station sends the UE the radio between ρA and ρB as a cell-specific value and a parameter for use in determining ρA as a user-specific value. In the LTE system, the base station provides the UE with the power ratio information between the pilot and data signals, and the UE is capable of acquiring the information on the transmit powers of the CRS and data signals for use in data modulation. The base station transmits data and RS signals that are adjusted according to the power ratio information provided to the UE.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.